The overarching theme of the HIV Center ? The Science of Ending the HIV/AIDS Epidemic (EtE): Efficacy to Effectiveness ? demands innovative study designs and state-of-the-art analytic strategies. These include rigorously designed trials to evaluate prevention interventions and treatment paradigms among the most vulnerable populations in single-site or multi-site studies and implementation trials in which strategies for scale- up at the community level may be evaluated. Also critical are public-health scale trend analyses of epidemiologic surveillance data, social network analyses, and service utilization studies. Moreover, qualitative and quantitative assessment methodologies, including mixed methods, can provide key insights into a) challenges faced by high risk populations in reducing risk behavior and using HIV services; b) contexts of emergent risk situations; and c) case studies of treatment successes or failures. The Statistics, Assessment, and Data Management (StAD) Core will be a resource for cutting-edge conceptualization, consultation, and collaboration in major research methods critical to the Center's mission. The Core has three Specific Aims: (1) to develop and promote state-of-the-art research design and analytic strategies for study planning, analytic monitoring, and statistical analyses in bio-behavioral HIV/AIDS research; (2) to facilitate identification, adaptation, and/or development of assessment strategies that maximize validity, technological currency and flexibility, and explanatory power; and 3) to promote rigorous data management. To achieve these aims, the StAD Core will implement a coordinated set of activities including triaged individual consultation on developing proposals, funded studies, and manuscripts; expert monitored analytical and data management support; participation in Cross-Core Meeting reviews; and didactic capacity-building activities, including seminars and workshops. In addition to providing intensive guidance on research designs, statistical approaches and assessment, we will leverage expertise in our institutional data management center to provide access to a state-of-the-art data management system that ensures and optimizes secure data collection, including real-time data quality checks and storage, and will build capacity for harmonizing existing and new data sets to enable meta-analyses, pooled analyses, pilot study research, and data sharing. StAD Core Members have complementary expertise in the design and conduct of clinical and behavioral intervention trials, the determinants studies that inform them, and state-of-the-art analytical strategies and data management systems. Core Director, Martina Pavlicova, Ph.D., an Associate Professor of Biostatistics at the Columbia University Mailman School of Public Health has experience overseeing statistical teams on HIV clinical trials and observational studies. Core Co-Director, Susan Tross, Ph.D., a long-time member of the Center is an Associate Professor in the Department of Psychiatry at NYSPI and Columbia University with expertise in assessing, developing and evaluating substance use and HIV risk interventions.